Heat treatment of track-rails.



1|. sTATEs PATENT oFFIcE.

cH'msTEn 'PETER sAN-DBERG, or LoNDoN, ENGLAND.

HEAT TREATMENT 015' TRACK-RAILS,

specification. of Letters Patent;

Patent-ea Aug, 2v, 191s.

Application filed August 13, 191'?. Serial No. 186,041.

In my United States Patent No.,1178352 v dated the 4th day of April 1916 I have def` scribed a process of hardening the head of a steel rail to a depth sufficient materially to prolong the life of the rail by cooling the head moderately rapidly through the critical range of temperature by means of an elastic fluid 0r vapor or atomized liquid, care being taken that the temperature to which Athe steel is cooled is such that any heat remaining in the mass will not raise it again .to the critical temperature. l

The process has hitherto been applied either to rails inthe heated condition in which they leave the rolls or to re-heated rails. In other words, the rails treated have been in a condition in which they may be` said to be reservoirs of heat, that is to say a condition in which the rate. of cooling of the portion under treatment has been iniuenced by the low gradient of temperature di'erence between the parts of the mass.

I have since discovered that the application of this processto track rails when they show more or less wear allows continued use -of rails which would otherwise have t0 be.

discarded, vbut the cost of taking up the rails and treating them is so great that there is little orv no advantage as compared with laying new rails. The process of the present invention, however, is less costly, since the rails are treated n situ. Furthermore,

"I find that there is considerable advantage in treating new rails. in situ, instead of treating them before they are laid;v for `the strains set up in themails during transport and laying, involving. loading andunloading, bending to proper curvature, making ished joints, and the like, seriously aectg.

when` the/ heat is applied locally over its the hardened portion ofthe head.

It was obvious that 1n treating rails situ it would 'be impossible to heat the whole be applied section by section, stepl by step,

but in continuous progression from end to end of the rail, in order that the necessaryv homogeneity may be attained. Nor cou'ld it be foretold whether .the required rate of.

cooling could be attained when the heat was thus applied locally to the steel, that isto say when the rail to be treated was only heated a small portion ata time so that there was a steep gradient of temperature between the small portion heated above the critical temperature and the whole of the rest of the mass. Analogy indicated thatv under'such conditions, the rate of cooling would be much. too rapid; for it is known that by 'locally heating the surface of a steel plate or other article to the requisite temperature, discontinuing the heating before the rest of the mass has become unduly heated by conduction and allowing the. whole to cool, an extremely hardskin or face sharply differentiated in structure from the rest o f the mass is produced, showing that, even when unaided by artificial means, the cooling is so rapid that a thin skin of very hard structure is produced.

Indeed, it has electric arc, impinging upon a steel surface which is to be hardened, is caused to travel continuously over the surface followed immediately by a jet of cooling agent directed upon the heated spot, the heat penetratesonly to a slight depth'andthat it is necessary that the heated spot should be surrounded by metal to take up by compression the expansion of the said spot, as otherwise cracks and distortion would ensue.

It may be remarked. here that such a skin- -hardened surface, when subjected to shock it is .readily possible .t0 .attain the desired rate of cooling directly to produce the requisite hard-,structure in the head of the rail whole width, if the temperature of the head to a comparatively considerable depth is been shown that when an raised above the critical range by a source vof heat, such as a flame low in oxygen er otherwise insufficiently hot to burn or melt the steel in carrying out the process.

MyA experiments have also proved that when the heat is applied locally to a comparatively considerable depth in the head of the rail in the manner described and the steel is cooled with water, the hard structure is formed to a considerable depth in the steel and gradually merges through various intermediate structures to the normal pearlitic structure of the main body; this hard structure, though capable of turning the edge of Tthe normal structure of the mass.

An impression test Was then taken on each piece by forcing a hard steel ball 19 imn. diameter intothe surface of the several portions under a pressure of tons (a usual specification test for rails), with the following results N o. l. An impression was made of a depth of 3.6 mm.

No. 2. An impression was made of a depth of 3.4 mm.

No. 3. No impression at all, but the ballwas crushed.

rl `his shows very clearly the difference in res1stance to crushing between a thin and thick hardened layer on the surface of the rail, for whereas No. 2 showed very little 1mprovement over the untreated rail, the ball could make noLimpression on No.3 and 1n fact was kitself destroyed, although the hardness at tde surfaces of Nos. 2 and 3 was the same.

Another difficulty that had to be overcome 1n treating rails n situ was that due to eX- pansion and contraction ofthe rails owing to the heating and cooling of them. This has been completely overcome, in the first place by heating only a very small length of the head at one time, and in the second place l by completely cooling the rail immediately after treatment, so that the heat is not conducted to the web and the flange or base of the rail. For the latter purpose, where the rail is first cooled by air, after the temperature has been reduced below the critical, it sl at once completely 'cooled by water or the 1 ze. 'f

Still/another difficulty in connection with dium,

tramway rails wasdto prevent the destruction of the paving blocks, whether of wood or stone, immediately adjacent to the treated rail. At first these were destroyed by the heat, but 4it was found by experiment that by covering them with a suitable non-conduct-ing material such as clay, sheet asbestos or the like, they were completely protected and not affected by the heat in any way.

It is to be understood that what is aimed at in the present invention is not in any sense to produce a mere skin hardening effect, but to produce a rail having a hard structure to a depth which is variable at will within certain limits, and which does not cease suddenly but merges gradually into the normal structure of the main body ofl the steel comprised in the rail.

In carrying out the invention, to heat the rail or its surface any suitable source of heat may be employed, such as a gas or oil or spirit flame, a gas flame of medium heat being generally preferable as care must be taken that while it should be possible where required to heat the steel well below the surface, it is not caused 4to burn, melt or flow. An ordinary blow pipe flame or an oX'yacetylene flame low in oxygen, is for instance, suitable; or, for the same purpose, a very hot flame may be employed with a shield or sheath of more or less refractory material interposed between the flame and the rail.

Whether, an intermediate, tougher structure or a very hard, less tough structure is to be formed in the rail it is necessary to heat the steel until a layer of comparatively considerable depth has been "raised above the critical range. in the first case, this is necessary to obviate the formation of a very hard structure in the rail owing to the rapid conduction of the heat to the rest of the mass; and in the second case it is necessary to permit, on cooling, of the production in the rail of the gradual change in structure from Very hard at the surface to the normal pearlitic in the main mass, as distinguished from the shap differentiation produced when only a thin skin is very rapidly heated with a very hot flame.

To temper the rail or to produce an intermediate s'tructure therein, the rail may be cooled in the manner described in my prior patent above referred to, or, where a ve hard structure is to be produced the rail may be cooled with water, brine or the like.

The processes of heating and cooling are inl practice carried on continuously. For this purpose the source of heat, such as the burner 0r burners, and the cooling agent are gradually moved along the rail.

The burner or burners and the cooling devices are so arranged that the cooling-inewhethg'r air or Water or otherwise, is directed on to the rail as closely behind the flame or llames of the burner or burners as possible-and where water is employed an air j et may if desired be interposed between the ame and the water to maintain the rail free of water at the point where the flame is actually playing upon it, or to prevent th'e collection of water in' the groovel of the rail at that point. If desired, also a jet of air* or water may be caused to impinge on the rail in advance of the flame, to prevent the heating of .the rail too far in advance, as, for instance, in joining up to a place where the rail has been already treated.

One greatadvantage of the processI is that it tends to take out of the head of the rail the strains produced therein by rolling, f straightening and bending. l Suitable apparatus for practising the invention forms the subjectof my application for United States Letters Patent Serial No. 186,042 of even date-herewith. A simple and convenient form of said apparatus is, however, illustrated in the ac-l companying drawings, the single vfigure of p which is a side elevation.`

In the construction disclosed a platform a is suitably mounted on flangedwheels b 'adapted tofrun in the rails 'and upon the platform is mounted gearing adapted to be operated by hand to move the car alng.

'As shown, the gearing comprises a handle c,

worm d rotated thereby, worm-wheel d1, shaft e, chain-wheel e1 thereon, and chain e2 driving gdirect on to the Ychain-wheel e3 on the driving axle b1; A brake b2 operated by the hand-wheel b3 and screw stem b4 is, preferably, provided on the car. Upon the car or truck and preferably between the Wheels is arranged a burner of suitable con- 40 struction. As shown, this consists of Va blow pipe f, which, forthe purpose ofregulating or adjusting the distance of the jet vabove the rail is mounted upon va pivot g about whichlthe burner f can be turned byA means of the screwstem h and regulating wheel j.' The burner f is connected by `flexible piping cwith gas cylinders Z carried upon the car or 4truck to supply the burner. Behind the burner f is arranged an air jet m for the purpose of blowing air on to the hea-ted rail, and behindthe air jet is arranged ay water jet a, for directing water on to the rail. The air jet m may be supplied with air from a blower operated either by hand or automatically andcarried on the car a in any convenient position or arranged independently thereof. Such blower may convenientlyl be electrically driven. The water jetl n may be supplied with `water 50 from a tank nl on the car, as shown, or froml an independent source such as an ordinary water cart or hydrant in the road. f

In operation, the car is moved forward slowly, the burner-projecting a flame on to f5 ythe railitolieat it land.: the heated rail being sides of the car.

Having thus described the nature of the said invention and 'the best means I know of carrying the same into practical effect, I

claim 1. A method of hardening or tempering 'l5 A track rails in situ so as to produce in the headof the rail a hard structure which eX- tends from the. wearing surface into the mass of metal and merges gradually into the normal structure of the main body of the steel, which' method consists in moving slowly and continuously along the surface ofthe rail a source of Vheat iadapted to direct thel heat against a verygsmall portion o f the wearing surface but to heat said surface over its whole width and to heat the head of the rail tg a desired,l andin any c ase considerable, depth to ai temperature .above the critical range and directing acooling medium on to the rail'immediately in 90 the rear of. the source of heat to cool 'the rail to a temperature below the critical.

2. A methodlof hardening or tempering track -rails n situ 'so as to produce 1n the Aheadl of therail -a hard structure which eX- Y tends from the wearing surface into the mass of metal and merges gradually into the ynormal structure of the main body of the steel, which method consists in moving slowly and continuously along the surface of the rail a source. of heat adapted to direct the heat against a very .small portion of the wearing surface but vto heat said surface d over its whole width and to heat the head of the rail to a desired, and inany case con- 10@ siderable, depth to a temperature above the critical range andl cooling the rail moder- -ately` rapidly immediately in the rear of the source 4of heat to a temperature below the critical 'by means of a flowof cooling agent. 110

3. 'A method' of hardening or tempering -track rails n situ' so as to produce in the head of the rail a hard structure which eX-.

tends from the wearing surface into the mass of metal and merges -graduallyinto 115.

the normal structure of the main bodyl of the steel, which method consists vin moving slowly'and continuously along the surface of the rail a source' of heat adapted to direct theheat against a very small portion of the' '120 lwearing surface but' to heat said surface overits whole width and to heat the head vof the rail to a desired, and in .any case,

considerable, depth to a temperature above I the critical range and cooling the rail immediately in the rear of the source of heat.

4. A method of hardening or tempering track rails in -sz'tu so as to produce in the head of the rail a hard structure which extends from the wearing .surface into the mass of metal and merges gradually into the normal structure of the main body of the steel, Whichmethod consists in -moving slowly and continuously along the surface of the rail a source of heat adapted to direct the heat against a very small portion of the Wearing surface but to heat said surface over its Whole WidthV and to heat the head of the rail to a desired, andin any case, considerable', depth to a temperature above the critical range and cooling the rail immediately in the rear of the source of heat bydirecting at the same time and n` close succession a blast of elastic uid and a jet of cooling liquid -on to the rail,

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses. v

` CHRISTER /PETER SANDBERG.

Witnesses:

E. S. ORMSBY, L. M. NEwnANns. 

